does a rcd provide porotection against fire?

[chrisreid186]

ok remember being told that a RCD will provide protection against fire

however I've came across 2 situations where the circuit is protected by a rcd and a fire could of easily started.

first situation where a builder was using a wind up extension lead (not fully unwound) to feed a portable heater, the extension lead plug was badly burnt

the second was at a flat where the night storage heater didn't work, had a look at the c.u and noticed a burnt out chock block on the live, after taking a closer look someone had extended the 2.5mm live with 1mm back to the mcb

now with that in mind am i right saying a rcd will only provide protection against fire if the live/neutral conductor touches earth??

cheers for your help

still learning

 

[telectrix]

does not necessarily have to touch. just needs sufficient breakdown of the insulation to give rise to sufficient leakage current ( eg 30mA) to activate the RCD.

 

[Marvo]

The RCD might or might not trip after a fire has started. It's only there to protect the user of the installation from electric shocks.

 

[chrisreid186]

when you say it doesn't need to touch is this because of induction or arching or both?
is that also the reason why we use a 500v insulation resistance test rather then a lower voltage, 500v can produce a arc/induction and lower voltages cant??

 

[RogertheBodger]

An RCD can't protect against fire in the examples you are giving,

The extension lead plug was most probably burnt due to being severely overloaded or a bad connection inside the plug top.
The RCD would only operate in this case if the burning became bad enough for the cpc to melt into a live conductor.

In the CU example the undersized 1.0mm would have become hot, maybe infected the connector, causing the burning, in this case the RCD would only trip if the heat from the conductor had caused it to fuse with another conductor or earth, in the CU

 

[Marvo]

In a standard domestic electrical installation none of the devices installed are directly designed to protect against fire, only indirectly by virtue of overload prevention. The best fire protection you can get is if the installation is compliant with the regs and it was installed by an experienced electrician who has made his terminations secure and not overtightened the wire screw-connections in the plugs for example.

 

[Knobhead]

The basic answer is NO!
A properly rated MCCB along with a RCD will give some protection.
Nothing will give total protection!

 

[Deleted member 26818]

I understand that data collected by the ESC indicates that in 2007, 20% of fires caused by electrical appliances would have been avoided by the use of an RCD.

 

[Knobhead]

Correction there is a way around it!
A double wound isolation transformer with a voltage injection system on the secondary.
If you want to go down that road I hope you’ve very deep pockets!